In order to minimize the loads that are applied on a lifting surface of an aircraft during a maneuver or an atmospheric disturbance, it is known practice to implement a method which makes it possible to protect the structure of the aircraft by alleviating the loads. In fact, in maneuvering or in turbulence, the lifting surfaces of the aircraft undergo structural distortions, for example flexural and torsional, that can weaken the structure of the aircraft.
The methods currently implemented are based on load alleviation laws of a lifting surface, commonly referred to as “Maneuver Loads Alleviation” and “Gust Loads Alleviation”. These laws are devised from computations or theoretical simulations of loads, from flight parameters of an aircraft in a maneuver or an atmospheric disturbance. The simulations make it possible to determine thresholds of activation of these laws which are a function of theoretical flight parameter values. The latter can be the weight of the aircraft, the speed, the flight altitude, the Mach number, etc. The laws are activated when a set of flight parameter values measured during flight is equal to a set of flight parameter values determined in simulations. Subsequently, a control unit of the aircraft displaces or imposes a lock on the control surfaces associated with the lifting surface to reduce the loads thereon.
This solution is based on a theoretical behaviour of the aircraft in maneuvering or in turbulence and does not necessarily correspond to the real behaviour of the aircraft. Furthermore, this solution is time-consuming, because it requires new simulations to be carried out when the controls or the configuration of the aeroplane are modified in order to determine new theoretical activation thresholds. Furthermore, when the flight control laws or the configuration of the aircraft are modified, that entails a lengthy step of verification and adjustment of the load alleviation laws.